A rotating reel is mounted on a harvesting device for a harvesting machine to guide the crop to a cutting means as well as, if necessary, a feeding shaft. The reel includes a plurality of tine rods extending transversely to the direction of travel with protruding tines for engaging the crop. The reel is basically supported by the supporting pipe in the centre of the reel, the longitudinal axis thereof forming the rotational axis of the reel.
Fundamentally, the demand for larger, especially broader, headers for self-propelled harvesters is growing in the agricultural machinery industry. In particular the width, i.e. the dimension of the header transversely to the direction of travel, determines the time required for the harvesting process, as the field can be harvested in less time and with less runs with a wider header. However, an increase in the working width can reduce the stability of the overall construction, since the stress on the material depends on the quantity of material used.
The same applies for producing a reel which extends over the overall width of the header. While the machine is in operation, the mounted reel is exposed to increasing tensile and compression forces. In relation to the desired crop yield, an excessive bending of the reel is not desirable, as this would vary too much the distance between the crop and the reel, leading to different cutting results over the width of the reel.
Currently, the tensile and compression forces which occur are almost fully absorbed by the central supporting pipe of the reel. Any increase on the stress on the material of the supporting pipe, depending on the reel dimension, must be compensated by reinforcing the supporting pipe. This is achieved by either increasing the pipe diameter or using alternative materials, which however often leads to a significant increase in the weight of the reel or an enormous increase in cost. In addition, the increase in weight increases the occurring bending forces and worsens the energy balance of such harvesters, since an increase in weight usually brings higher fuel consumption for the harvester.
Consequently, there is a major concern in the development of harvesting equipment and reels to achieve a maximum total weight reduction without being penalized by a sensitive increase in development costs or production costs.